WASHINGTON, Sept 28: US military chief Admiral Mike Mullen called the Pakistani military leadership on Tuesday and assured them that Washington respected Pakistanâ€™s sovereignty and territorial integrity.

The calls, diplomatic sources said, were made after Pakistan lodged strong protests against a series of attacks by the US-led International Security Assistance Force during the last three days, and conveyed to the United States that if forces in Afghanistan continued to violate its territorial integrity it would be forced to consider appropriate response.

At Pentagon, spokesman Col Dave Lapan told journalists on Tuesday that recent cross-border air strikes by Nato helicopters in Pakistan might have violated procedures and resulted from â€œcommunication breakdownsâ€.

â€œI donâ€™t know that Iâ€™d call it a disagreement but there are certainly discussions under way between our forces and the Pakistanis about this particular incident,â€ he said.

Col Lapan said the talks were focused on â€œwhat were the communication breakdowns, what happened, what was supposed to happenâ€.

ISAF forces were not able to notify Pakistani officers about the helicopter strikes until after the operation, he said.

â€œI think I can say that clearly in these instances things didnâ€™t occur in the way that theyâ€™re supposed to. And thatâ€™s what weâ€™re trying to get to,â€ Col Lapan said. Isaf said in an earlier statement that the helicopters went after insurgents in Pakistan after an Afghan security forcesâ€™ outpost in the Khost province came under attack on Friday.

Diplomatic sources in Washington told Dawn that Pakistan had informed the Americans that while Islamabad was Americaâ€™s partner in the war against terror, â€œthey are very sensitive to their sovereignty and territorial integrityâ€. The Pakistanis insisted that the UN and Nato mandate for operating inside Afghanistan ended on the Afghan border and â€œit does not cover an inch of Pakistani territoryâ€.

The Pakistanis said that they were still investigating the three incidents to see if the helicopters fired their weapons from the Afghan territory or physically entered Pakistan.